Manufacture of hydrogen peroxide



Reissued June 21, 1938 UNITED STATES PATENT OFFICE MANUFACTURE OFHYDROGEN PEROXIDE Edward C. Soule, Niagara Falls, N. Y., assignor to TheMathieson Alkali Works, Inc., New York, N. Y., a corporation of VirginiaNo Drawing. Original No. 2,035,101, dated March 24, 1936, Serial No.737,044, July 26, 1934. Application for reissue January 5, 1937,

Serial No. 119,122

8 Claims.

My invention relates to improvements in the production of hydrogenperoxide by oxidation of hydrazo compounds.

Hydrogen peroxide can be produced by oxidation of a number of organiccompounds. As applied to some of these compounds, the oxidationproduces, in addition to hydrogen peroxide, an oxidized compound whichcan be reduced to the original compound subjected to oxidation. Hydrazobenzene is one such compound. Oxidation of hydrazo benzene produceshydrogen peroxide and azo benzene, and the azo benzene can be reduced toproduce hydrazo benzene.

The availability of such compounds as intermediates in the production ofhydrogen peroxide is, however, limited by the attainable chemicalefficiencies of the reactions involved in successive oxidations andreductions.

For example, if hydrazo benzene, in solution in benzene, is oxidized byvigorous agitation in the presence of oxygen and of a limited amount ofwater, the reaction rate is so slow, even at temperatures as high as C.,that 7 to 8 hours may be required for oxidation of as much as of thehydrazo benzene. The reaction rate is increased by making the aqueousmedium present alkaline, but this alkalinity also renders unstable thehydrogen peroxide produced. Due to the long period required foroxidation of any substantial part of the hydrazo benzene, secondaryreactions between hydrogen peroxide and hydrazo benzene proceed to apoint such that the chemical efiiciency may drop to 50% or less.

I have discovered that by using amino substituted aromatic hydrazocompounds, remarkable increases in reaction rates are realized and thathigh chemical efliciencies can be thus attained. For example, I havebeen able to pro duce substantially theoretical yields of hydrogenperoxide in reaction periods of 10 to 15 minutes using amino substitutedaromatic hydrazo compounds under conditions such that but 40% yields ofhydrogen peroxide were produced in reaction periods of 16 hours usinghydrazo benzene.

In carrying out my invention, I prepared the amino substituted aromatichydrazo compound by reduction of the corresponding azo compound underappropriate conditions, using, to effect the reduction, for example,sodium amalgam and water or zinc and an aqueous solution of sodiumhydroxide. The amino substituted aromatic hydrazo compound isconveniently produced in solution in a solvent such as benzene ortoluene. Losses by oxidation are avoided by carrying on the reduction inan inert atmosphere, an atmosphere of nitrogen or of hydrogen forexample. Following the reduction, if a solvent immiscible with watersuch as benzene or toluene is used, I separate the solution of the aminosubstituted aromatic hydrazo compound from the aqueous materialremaining after the reduction. Any entrained sodium hydroxide iseliminated from the solution, for example, by washing it with water oran acid aqueous medium, an acid salt or an acid or an acid solution of asalt, sodium sulfate for example, or by filtering the solution through,for example, an acid salt such as sodium acid sulfate or other solidabsorbent for sodium hydroxide.

I carry out the oxidation of the amino substituted aromatic hydrazocompound, in accordance with my invention, in the presence of an amountof water, or of an aqueous medium rendered acid by the addition, forexample, of sulfuric acid or phosphoric acid, limited to produce ahydrogen peroxide solution of the desired concentration. I add the aminosubstituted aromatic hydrazo compound to such an aqueous medium inamount so limited, replace the inert atmosphere by an oxidizingatmosphere, an atmosphere of oxygen or of air for example, and effectthe oxidation by vigorous agitation in this atmosphere. At temperaturesof 20-25 0., reaction periods of 10 to 15 minutes are usuallysufl'icient. Advantageously the oxidation of the amino substitutedaromatic hydrazo compound is efiected while maintaining the pH of thereaction medium at a value not exceeding 8. Any coloring matter presentin the aqueous solution of hydrogen peroxide produced can be removed byfiltering it, for example, through an absorbent such as charcoal.Hydrogen peroxide solutions containing as much as 50%-60% or more H202by Weight can be so produced. The azo compound produced by theoxidation, after separation from the aqueous solution of hydrogenperoxide produced, is reduced for re-use in a repetition of the process.

My invention will be further illustrated by the following examples ofoperations embodying the use of various amino substituted aromatichydrazo compounds in accordance with my invention.

Example I.-50 parts (by weight) of 2 amino 5 azo toluene dissolved in8'79 parts (by weight) of benzene was reduced by the action of 10.5parts (by weight) of sodium, as sodium amalgam, in the presence of 100parts (by Weight) of water in an atmosphere of hydrogen.

The benzene solution of the corresponding hydrazo compound was separatedfrom the mercury and the aqueous material and, after separation, waswashed free of sodium hydroxide by water from which dissolved oxygen hadbeen displaced by hydrogen. 25 parts (by weight) of water were thenadded to the benzene solution and the mixture was vigorously agitatedfor 30 minutes in an atmosphere of oxygen at a temperature of 20-25 C.An aqueous solution of hydrogen peroxide containing 91% of thetheoretical yield was recovered by separation from the resulting benzenesolution of the original azo compound.

Example II.20 parts (by weight) of 4 dimethyl amino 1 azo benzenedissolved in 866 parts (by weight) of toluene was reduced by the actionof sodium amalgam in the presence of water in an atmosphere of hydrogen.The toluene solution of the corresponding hydrazo compound was separatedfrom the mercury and the aqueous material, and, after separation, waswashed free of sodium hydroxide by water from which dissolved oxygen hadbeen displaced by carbon dioxide. 10 parts (by weight) of water werethen added to the toluene solution and the mixture was vigorouslyagitated for 10 minutes in an atmosphere of oxygen at a temperature of2025 C. An aqueous solution of hydrogen peroxide containing 75% of thetheoretical yield was recovered by separation from the resulting toluenesolution of the original azo compound.

Example III.11 parts (by weight) of amino azo xylene dissolved in 483parts (by weight) of benzene was reduced by the action of sodium amalgamin the presence of water in an atmosphere of hydrogen. The benzenesolution of the corresponding hydrazo compound was separated from themercury in the aqueous material and, after separation, was washed freeof sodium hydroxide by water from which dissolved oxygen had beendisplaced by carbon dioxide. 10 parts (by weight) of water were thenadded to the benzene solution and the mixture was vigorously agitatedfor 10 minutes in an atmosphere of oxygen at a temperature of 20-25 C.An aqueous solution of hydrogen peroxide containing 72% of thetheoretical yield was recovered by separation from the resultingsolution of the original azo compound.

Exdmple IV.30 parts (by weight) of 4 dimethyl amino benzene 1 azo lnaphthalene dissolved in 440 parts of benzene was reduced by the actionof sodium amalgam in the presence of water in an atmosphere of hydrogen.The benzene solution of the corresponding hydrazo compound was separatedfrom the mercury and the aqueous material and, after separation, waswashed free of sodium hydroxide by water from which dissolved oxygen hadbeen displaced by hydrogen. 25 parts (by weight) of water were thenadded to the benzene solution and the mixture was vigorously agitatedfor 10 minutes in an atmosphere of oxygen at a temperature of 20 25 C.An aqueous solution of hydrogen peroxide containing 59% of thetheoretrical yield was recovered by separation from the resultingbenzene solution of the original azo compound.

Example V.-35 parts (by weight) of 4 amino benzene 1 azo benzenedissolved in 866 parts (by weight) of toluene was reduced by the actionof sodium amalgam in the presence of water in an atmosphere of hydrogen.The toluene solution of the corresponding hydrazo compound was separatedfrom the mercury and the aqueous material and, after separation, waswashed free of sodium hydroxide by water from which dissolved oxygen hadbeen displaced by carbon dioxide. 15 parts (by weight) of water werethen added to the toluene solution and the mixture was vigorouslyagitated for 15 minutes in an atmosphere of oxygen at a temperature of2025 C. An aqueous solution of hydrogen peroxide containing 65% of thetheoretical yield was recovered by separation from the resulting toluenesolution of the original azo compound.

Example VI .10 parts (by weight) of 2 amino azo anisole dissolved in 440parts (by weight) of benzene was reduced by the action of sodium amalgamin the presence of water in an atmosphere of hydrogen. The benzenesolution of the corresponding hydrazo compound was separated from themercury and the aqueous material and,

after separation, was washed free of sodium hydroxide by water fromwhich dissolved oxygen had been displaced by carbon dioxide. 25 parts(by weight) of water were then added to the benzene solution and themixture was vigorously agitated for minutes in an atmosphere of oxygenat a temperature of 2025 C. An aqueous solution of hydrogen peroxidecontaining 77% of the theoretical yield was recovered by separation fromthe resulting benzene solution of the original azo compound.

I claim:

1. In the production of hydrogen peroxide, the improvement whichcomprises oxidizing an amino substituted aromatic hydrazo compound inthe presence of an aqueous medium.

2. In the production of hydrogen peroxide, the improvement whichcomprises oxidizing an amino substituted aromatic hydrazo compound inthe presence of an aqueous medium having a pH not exceeding about 8.

3. In the production of hydrogen peroxide, the improvement whichcomprises oxidizing an amino substituted hydrazo benzene in the presenceof an aqueous medium.

4. In the production of hydrogen peroxide, the improvement whichcomprises oxidizing an amino substituted hydrazo toluene in the presenceof an aqueous medium.

5. In the production of hydrogen peroxide, the improvement whichcomprises oxidizing an amino substituted hydrazo xylene in the presenceof an aqueous medium.

6. In the production of hydrogen peroxide, the improvement whichcomprises oxidizing an amino substituted hydrazo naphthalene in thepresence of an aqueous medium;

7. In the production of hydrogen peroxide by cyclically reducing anazo-type compound and oxidizing the resulting hydrazo-type compound in asolvent in which the azo-type compound is soluble but in which thehydrogen peroxide formed is insoluble, the oxidation being effected withan oxygen containing gas and the reduction being effected in an alkalinemedium, theimprovement which comprises separating the hydrazo solutionfrom the major portion of the alkaline medium in which the reduction wasefiected and treating the separated hydrazo solution to eliminateentrained free alkali prior to the subsequent oxidation of the hydrazosolution.

8. In the production of hydrogen peroxide by cyclically reducing anazo-type compound and oxidizing the resulting hydrazo-type compound in asolvent in which the azo-type compound is soluble but in which thehydrogen peroxide formed is insoluble the oxidation being effected withan oxygen containing gas and the reduction being effected in an alkalinemedium, the improvement which comprises separating the hydrazo solutionfrom the major portion of the alkaline medium in which the reduction waseffected, treating the separated hydrazo solution to eliminate entrainedfree alkali prior to the subsequent oxidation of the hydrazo solution,and thereafter effecting the oxidation in the presence of an aqueousmedium having a pH not exceeding about 8.

EDWARD C. SOULE.

